I use the CBFM - used it to get pregnant with my son back in 2007. Broke it out and dusted it off when we started TTC#2 last April. It helped me catch my O time and get pregnant 3 times since then, though sadly they all ended in MC.
You should BD whenever you have High and Peak readings. Also, the first cycle you use it, there is a chance it will NOT pick up your peak ovulation as it is getting used to your body and your hormone levels. That's okay...you can actually "read" the sticks, though it says not to. If you see 2 lines of equal color (usually faint - like a light blue) this usually means you are in the peak period and you should get to BD'ing.
Good luck!!!